Process for light naphtha upgrading



D. D. M LAREN PROCESS FOR LIGHT NAPHTHA UPGRADING May 17, 1960 5 Sheets-Sheet 1 Filed March 1, 1957 Donald D. MocLoren Inventor y Attorney May 17, 1960 D. D; M cLAREN PROCESS FOR LIGHT NAPHTHA UPGRADING 5 Sheeis-Sheet 8 Filed March 1, 1957 FIGURE 4 EEEE M0000 05 n 2 wwwm w Emmmm m SSSS l WPPPP S T fiwm llm P22 w 'm v O0AA 8 ||I|9 w 5 9 a 0 OCTANE NUMBER, RESEARCH CLEAR Donald D. MocLoren lnyentor By Attorney May 17, 1960 D. D. MacLAREN PROCESS FOR LIGHT NAPHTHA UPGRADING 5 Sheets-Sheet 4 Filed March 1, 1957 FIGURE 5 -240 PSIG. 950E -24O PSIG 975E PRESSURE TEMP 9 90 A -3oo PSIG. 950 F. A -3oo PSIG 915 F o a m 0-, PARAFFIN CONV Donald D. MocLoren Inventor By 1 Attorney May 17, 1960 D. D. M LAREN 2,937,137

PROCESS FOR LIGHT NAPHTHA UPGRADING Filed March 1, 1957 5 Sheets-Sheet 5 Inventor mQ O mO N9 O 09 mm mm mm mm mm Om J mm Om Ob Ow Om 051 com I 4 Qwm com I 4 onhm Qmm OWN Q comm Qmm OVN I O %"lOA-G'I3IA o Donald D. MocLoren By Attorney manor.

. aluminate spinel.

United States Patent 2,937,137 7 PROCESS FOR LIGHT NAPHTHA UPGRrSDING Donald D. MacLaren, Scotch Plains, N.J., assignor to Esso Research and Engineering Company, a corporalion of Delaware Application March 1, 1957, Serial No. 643,343 8 Claims. (Cl. 208-138) upgrading light naphtha fractions to produce high octane number motor fuels in high yields. More particularly, it relates to obtaining a maximum yield octane relation .when processing light naphthas boiling in the range of about C /200 F. by using process conditions to obtain maximumraromatics yield by operating at only enough severity to give just 100% C conversion thus minimizing C conversion. and of the hydroformate may be used to select these process conditions. The hydroformate is then processed to separate out the small amount of n-C, and C parafiins which have low octane rating. These are recycled to the reaction zone or are used in high quality jet fuels or other specialty products. By this process a 19 to 23% increase in yield (over conventional platinum hydroforming) of C motor fuel material at 100 octane level is obtained.

Hydroforming is a well known and widely used process for upgrading hydrocarbon fractions boiling in the motor gasoline or naphtha boiling range toincrease their octane numbers and to improve their burning or engine cleanli- In hydroforming, the hydrocarbon ness characteristics. fraction or naphtha is contacted at elevated temperatures and pressures and in the presence of hydrogen or. hydrogen enriched process gas with solid catalytic materials under conditions such that there is no net consumption of hydrogen and ordinarily there is a net production of hydrogen in the process. A variety of reactions occur during hydroforming, including dehydrogenation of naphthenes to the corresponding aromatics, hydrocracking of parafiins, isomerization of straight chain paraflins to form branch chain paraffins, dehydrocyclization of par'aifins and isomerization of compounds such as ethylcyclopentane to form methylcyclohexane which is readily converted to toluene. In addition to these reactions, some hydrogenation of olefins and polyolefins occur and sulfur or sulfur compounds are eliminated by conversion to hydrogen sulfide or to catalytic metal sulfides making the hydroformate burn cleaner or form less engine deposits when used as the fuel in an internal combustion engine.

Hydroforming operations are ordinarily carried out at temperatures of 750-1l50 F. in the pressure range of about 50 to 1000 pounds per square inch and in contact with such catalysts as molybdenum oxide, chromium oxide, or in general, oxides or sulfides of metals of groups IV, V, VI, VII and VIII of the periodic system of elements alone, or generally supported on a base or spacing agent such a alumina gel,,precipitated alumina or zinc A good non-precious metal hydroforming catalyst is one containing about wt. percent molybdenum oxide upon an aluminum oxide base prepared by heat treating a hydrated aluminum oxide or upon a zinc aluminate spinel. A good precious metal hydroforming catalyst is one employing an alcoholate (eta) alumina base carrying 0.6% by weight of platinum. Catalysts of lower platinum content may also be used as may also silica stabilized alumina base catalysts."

Chromatographic analysis of the feed 2,937,137 Patented May 17,

ice

It has been proposed in U.S. Pat. 2,689,823, September 21, 1954, to effect the hydroforming of naphtha fractions in the presence of a dense fluidized catalyst mass in a fluidized solids reactor system in which naphtha vapors 5 are passed continuously through the dense fluidized bed of hydroforming catalyst particles in a reaction zone, spent catalystv particles being withdrawn from the dense bed in the reaction zone and 'passed to a separate regeneration zone where inactivating carbonaceous deposits are removed by combustion, whereupon the regenerated catalyst particles are returned to the main reactor vessel. Fixed bed hydroforming, of course, is conducted by passing the naphtha vapors through a fixed bed of catalyst and if regeneration is required, shutting down the particular reactor, purging to remove reactant vapors, wan drawing the catalyst or regenerating by passing an ox gen-containing gas through such catalyst bed.

Hydroforming is usually applied to a rather wide boiling range naphtha, i.e. to one having a boiling range of'from about 125 F. to about 400-430 F. Ithas been known that the lower boiling naphthas are not substantially improved by hydroforming processes as ordinarily conducted. The extensive report entitled An Appraisal of Catalytic Reforming in Petroleum Processing for-August 1955, for example, states at page 1174: Optimum reformer utilization is obtained by'not using feed stock constituents boiling much below 200 F. which do not contribute greatly to increased octane during reforming as these merely take up reformer capacity better usedfor high boiling materials more suitable to octane upgrading. In view of the continuing demand for more and higher octane number gasolines, however, it isbecoming increasingly important to upgrade these lower boiling naphtha fractions.

It is the object of this invention to provide the art with an improved method for hydroforming or upgrading light naphthas.

It is also the object of this invention to provide a simple, efiective method for upgrading light naphthas boiling in the range of from about 100-200 F., preferably from about 100-180 F. to form high octane products in high yields.

These and other objects will appear more clearly in the detailed specification and claims which follow and in the accompanying system designed to carry out the present invention and in which Figures 2-6 present an analysis of chromatographic data obtained on a 0 -200 F. cut light naphtha processed by platinum hydroforming at pressures in the range of -300 pounds.

From this data it has now been found that there is an optimum conversion level to which hydroforming should be carried. Above this conversion level aromatics are destroyed and high octane iso C s are cracked away. The accompanying Figures 2 and 3 illustrate this destruction of aromatics occurring above the optimum octane level of about 95 octane, and that a maximum yield; of aromatics occurs at that level.

Accompanying Figure 4 shows that this maximum occurs at the point where complete conversion of,the C parafiins has just been reached, Figure 5 shows that I this corresponds to about -80% conversion of the C paraflins and Figure 6 shows that if severity is increased further, C paraffins, especially iso C s are cracked away reducing high octane gasoline yield. Thus it can be seen 6 from these figures taken together that for platinum hydroforming optimum conversion is obtained at just 100% conversion of C parafiins which corresponds to '-75-80% conversion of C parafiins. This is the pointof maximum aromatic and total gasoline yields. It is seen 0 that above this level further octane improvement is ob tained only by cracking away the remaining C paraffins and at the sametime destroying C paraifinsand some l of the'aromatics already in the product.

Cracking of the C s is doubly disadvantageous in that the iso C parafiins are preferentially cracked.

According to the present invention it is proposed to take advantage of this optimum conversion by separating out from the product the nC and C paraffins. These may then be recycled to thehydroforming conversion zone or separately used as a component in high quality jet fuel or other specialty products. By this invention large improvements in yield of 100+ clear octane number motor fuels of the order of a 20% increase are obtained.

The advantages of this invention may of course be carried out in either fixed or fluid bed platinum hydroforming. In addition, however, fluid molybdenum oxide catalyst hydroforming is also susceptible to the method of this. invention. Thus similar chromatographic data under varying process conditions from fluid molybdenum oxide hydroforming would be obtained and reaction conditions would then be chosen so that conversion would be carried to the point of just 100% C conversion.

The invention of this application will be more clearly I understood by reference to Figure 1 which diagrammatically represents a system adapted to carry out the present invention.

Referring to this drawing, a C -200 cut light naphtha is supplied through line 1 past closed valve 2, through open valve 3 to distillation column 4. This column is operated to separate out a 180-200 F. bottoms fraction which is passed through line 5 to separate heavy naphtha hydroforming equipment not shown in which it may be more advantageously processed. From the top of column 4 the C -800 F. cut fraction is fed through line 6 to the light naphtha hydroformer 8. Alternatively, if desired, the entire C -200 F. light naphtha may be fed directly to the light naphtha hydroformer 8 by closing valve 3 and opening valve 2 in line 7. Conditions are set in the hydroformer to obtain maximum aromatics conversion and 100% conversion of C paraifins both with the minimum conversion of C paraflins. From hydroformer 8, product is passed through line 9 to suitable catalyst recovery equipment, if desired, or necessary, and is then passed through suitable heat exchanger and condenser equipment to gas liquid separator 10' wherein recycle gas is separated and passed through line 11 to compressor 12. From compressor 12 gas is recycled through line 13 back to the hydroformer. From separator 10 the liquid hydroformate is passed to stabilizer 15 wherein the C material is removed overhead through line 16 and is passed to conventional light ends recovery processing not shown. The bottoms from stabilizer 15 are fed through line 17 to deisopentanizer column 18. Isopentane is withdrawn from the top of this column through line 19 as one of the major products and the bottoms are passed through line 20 to superfractionator column 21. From the bottom of this superfractionator column benzene (or if the full C -200 F. feed was hydroformed then benzene and aromatics) are passed through line 22 as a major product of the process to blending facilities not shown for use with the isopentane in high octane motor fuels. From the top of the superfractionator 21 normal C and C paraflins are passed through line 23 past closed valve 24 through open valve 26 and line 27 back to line 6 for recycle to the hydroformer. Alternatively, if desired, valve 26 may be closed and these nC and C paraffins may be passed through open valve 24 and line from the system and used advantageously as a component in high quality jet fuel or other specialty productts. The main products from operation as proposed by this invention are isopentane and aromatics both of which have leaded octane numbers well over 100.

By following the teachings of this application the maximum yield of isopentane and aromatics possible in light 4 naphtha hydroforming will be obtained. For example, if it is desired, to make 100.5 clear octane from a C 180 F. Arabian feed by conventional once through operation in 300 pound platinum hydroforming a yield of 34.5% C material only is attainable. By the present invention, on the other hand, where the platinum hydroformer is operated at the optimum conversion of C paraffins with recycle of nC and C paraflins, an overall yield of 42.5% for the same octane number is attained. This is a gain of 8% on fresh feed in yield or based on such ordinary yield from conventional hydroforming an improvement in yield of 23%. At the same time the catalyst required in the hydroformer is greatly reduced; a feed rate of 1.0 wt. of feed/hr./wt. of catalyst being required by the conventional process and a feed rate of 1.7 wt. of feed/hr./wt. of catalyst being possible by the present process. This latter is very significant in view of the extremely high cost of the platinum catalyst used in platinum hydroforming.

Alternatively in processing a C -200 F. Arabian feed to 101.5 Research clear octane number conventionally by platinum hydroforming, a C yield of 31% is obtained. By the method of this application with separation out of the nC and C paraffin for use in other products a yield of 37% for the same 101.5 octane is obtained. This is an increase in yield of (3 of 6% on fresh feed or an improvement in yield of 19%. In addition again platinum catalyst requirements for the process are greatly reduced, i.e. 0.9 wt. feed/hr./Wt. of catalyst feed rate for conventional hydroforming and 2 Wt. feed/hr./wt. of catalyst feed rate for the present process.

The following example is illustrative of the present invention:

Example A C /200 F. light naphtha Arabian feed having an API gravity of 71.9 and a Research clear octane number of 59 is fed to a light naphtha fixed bed platinum hydroformer operating at 950 F. and 300 p.s.i.g. The platinum alumina catalyst contains 0.6% platinum on high surface area eta alumina derived from aluminum alcoholate and is in the form of x pills of a density of 47 pounds/cf. Recycle gas is supplied to the reactor at a rate of 3000 cubic feet per barrel of oil and the space velocity of the oil is 2.0 pounds of oil per hour per pound of catalyst in the reactor.

Stabilizer 15 is operated to remove the C material and deisopentanizer 18 is operated to separate overhead the isopentane main product of the process. Superfractionator 21 then separates the nC and C paraffin material overhead for use in other products leaving as bottoms the benzene, the other main product from the process. The isopentane and benzene fractions are then mixed to obtain a 37.0% (based on feed) yield of C material of 101.5 Research clear octane number.

It is to be understood that this invention is not limited to the specific example above which has been otfered merely as an illustration and that modifications may be made without departing from the spirit of this invention.

What is claimed is:

1. A method for upgrading light naphtha fractions boiling in the range of about C /200 P. which comprises hydroforming such feed at conditions of severity to obtain just 100% C normal and isoparafiin conversion, thereby minimizing C normal and isoparaffin conversion of about 75 to and attaining maximum aromatic yield; stabilizing such hydroformate to remove C and lighter material; fractionating to separate high octane isopentane product overhead leaving nC and C parafiins with benzene in bottoms of a column; superfractionating the bottoms from such column to obtain high octane benzene product as bottoms and an nC and C paraffins fraction overhead suitable for use in high quality jet fuels or other specialty products, this nC and C paraflins fraction being only a small amount of the total product.

2. The process as in claim 1 in which the catalyst used in hydroforming is platinum on high surface area alumina.

3. A method for upgrading light naphtha fractions boiling in the range of about C /200 P. which comprises hydroforming such feed at conditions of severity to obtain just 100% C normal and isoparafiin conversion, thereby minimizing C normal and isoparatfin conversion of about 75 to 80% and attaining maximum aromatic yield; stabilizing such hydroformate to remove C and lighter material; fractionating to separate high octane isopentane product overhead leaving nC and C paraflins with benzene in bottoms of a column; superfractionating the bottoms from such column to obtain high octane benzene product as bottoms and an nC and C paralnns fraction overhead and recycling such n and C paraflins fraction to the hydroforming conversion zone.

4. The process as in claim 3 in which the catalyst used in hydroforming is platinum on high surface area alumina.

5. A method for upgrading light naphtha fractions boiling in the range of about C 180 F. which comprises hydroforming such feed under conditions of only enough severity to obtain just 100% C normal and isoparaifin conversion thereby minimizing C normal and isoparafiin conversion of about 75 to 80% and attaining maximum aromatic yield; stabilizing such hydroformate to remove C and lighter material; fractionating to separate high octane isopentane product overhead leaving nC and C paraffins with benzene in bottoms of a column; superfractionating the bottoms from such column to obtain high octane benzene product as hottoms and an nC and C paraffins fraction overhead and recycling such nC and C paraflin fraction to the hydroforming conversion zone.

6. The process as in claim 5 in which the catalyst used in hydroforming is platinum on high surface area alumina.

7. A method for upgrading light naphtha fractions boiling in the range of about C 180 F. which comprises hydroforming such feed under conditions of only enough severity to obtain just 100% C7 normal and isoparafiin conversion thereby minimizing C normal and isoparafiin conversion of about to and attaining maximum aromatic yield; stabilizing such hydroformate to remove C and lighter material; fractionating to separate high octane isopentane product overhead leaving nC and C paraffins with benzene in bottoms of a column; superfractionating the bottoms from such column to obtain high octane benzene product as bottoms and an nC and C paraffins fraction overhead suitable for use in high quality jet fuels or other specialty products, this nC and C paraflin fraction being only a small amount of the total product.

8. The process as in claim 7 in which the catalyst used in hydroforming is platinum on high surface area alumina.

References Cited in the file of this patent UNITED STATES PATENTS 2,697,684 Hemmiuger et a1. Dec. 21, 1954 2,736,684 Tampoll Feb. 28, 1956 2,740,751 Haensel et a1. Apr. 3, 1956 

1. A METHOD FOR UPGRADING LIGHT NAPHTHA FRACTIONS BOILING IN THE RANGE OF ABOUT C5/200*F. WHICH COMPRISES HYDROFORMING SUCH FEED AT CONDITIONS OF SEVERITY TO OBTAIN JUST 100% C7 NORMAL AND ISOPARAFFIN CONVERSION, THEREBY MINIMIZING C6 NORMAL AND ISOPARAFFIN CONVERSION OF ABOUT 75 TO 80% AND ATTAINING MAXIMUM AROMATIC YIELD, STABILIZING SUCH HYDROFORMATE TO REMOVE C4 AND LIGHTER MATERIAL, FRACTIONATING TO SEPARATE HIGH OCTANE ISOPENTANE PRODUCT OVERHEAD LEAVING NC5 AND C6 PARAFFINS WITH BENZENE IN BOTTOMS OF A COLUMN, SUPERFRACTIONATING THE BOTTOMS FROM SUCH COLUMN TO ABTAIN HIGH OCTANE BENZENE PRODUCT AS BOTTOMS AND AN NC5 AND C6 PARAFFINS FRACTION OVERHEAD SUITABLE FOR USE IN HIGH QUALITY JET FUELS OR OTHER SPECIALTY PRODUCTS, THIS NC5 AND C6 PARAFFINS FRACTION BEING ONLY A SMALL AMOUNT OF THE TOTAL PRODUCT. 